1. Field of the Invention
The present invention relates to a field emitter using a diamond, and in particular to an improved diamond field emitter and a fabrication method thereof, capable of being applied to various uses such as a field emission display (FED) and a vacuum microelectronics, etc.
2. Description of the Conventional Art
Generally, an electron emission effect on a solid surface due to an electric field is a physical feature which enables various application of electron devices including a vacuum microelectronic devices and a microwave devices as well as a field emitter which is a flat-plate devices, etc. It is the most important subject in such various applications to obtain a field emission section having a good capability for emitting electrons when loading the field. The necessary characteristics for an excellent field emission section is that the emission of electrons can be easily and stably generated upon applying low voltage, the electron emission amount should be large, and long durability of the field emitter.
In order to achieve the above objects, developments of the field emission section is currently being processed in two ways. The first method is directed to induce the electron emission by centralizing electric fields at a tip portion which has a higher geometric curvature. The second method is related to utilizing a substance having a small value of a work function which is the necessary energy for discharging the electrons from a solid surface, as a material of the field emission section.
As an example for the former development, a method for fabricating a sharp tip of the field emitter using Si or Mo as a material, and using a dry-etching method or a special deposition method is known. The field emission effect of the field emitter section made according to this method has been confirmed, and such field emitter is currently being studied for applications to field emitting devices [H. F. Gray, Proc. 29th Int. Field Emission Symp., 38, 2355 (1991)].
In the second case, various useful materials for the field emission section have been studied and reported, and a diamond has been discovered as the best material thereamong. The reason is that a diamond has little or no energy barrier to the electrons to be emitted from the solid surface, and also when using the diamond as the material for the field emission section, the characteristic deterioration of the field emission is remarkably minute due to the superior mechanical, thermal and emission proof features of the diamond. In addition, the negative electron affinity of the diamond enables the process of fabricating the field emission section to be simple, because the electron emission is possible even though the diamond is in a flat-plate shape, not a tip shape, and also enable a durability of the field emitter to increase.
As discribed above, since the diamond has the negative electron affinity, the electron emission can be expected even though the field emitter is manufactured in the form of a flat-plate type. However, if the tip section of the field emitter is sharply shaped, a collection effect of electric field is increased, and large amount of the electrons are possibly emitted even when a low voltage is applied. Therefore, various attempts have been performed to accomplish such object. As an example thereof, there has been disclosed a method for coating a thin-film diamond on a tip formed of Si or Mo [N. S. Xu, Y. Tzeng and R. V. Latham, J. Phys. D26, 1776 (1993), V. V. Zhirov, E. I. Givargizov and P. V. Plenkhanov, J.Vac,Sci, and Tech., B13(2), (1995)]. However, in the above method, the density of the diamond nuclei is very low, thus it is hard to uniformly deposit the diamond film thereon, unless a special treatment is carried out on a surface of a substrate before the diamond deposition [A. A. Mosish and P. E. Pehrsson, Appl. Phys. Lett., 59, 417 (1991)], and it is difficult to uniformly coat the diamond film on the tip because the Si tip is easily broken during the process. Also, in order to increase the density of the diamond nuclei, another method known as a bias enhanced nucleation was provided by Yugo, Kimura, and Muto [S. Yugo, T. Kimura, and T. Muto, Vacuum, 41. 1364 (1990)], which is directed to increasing the density of the diamond nucleus by applying a DC voltage to a substrate in a plasma, however, in this method, it is also difficult to uniformly form the diamond nucleus over a large area. On the other hand, according to a method provided by Zhirnov, Givargizov, and Plenkhanov [V. V. Zhirnov, E. I. Givargizov, and P. S. Plenkhanov, J.Vac.Sci. and Tech., B13(2), (1995)] in which the diamond is deposited on a top of a tip section, but no special method is employed for the diamond nucleus formation, thus it is hard to deposit the diamond on a top of all tip section of the field emitter, and because the Si tip is not obtained by a process employing a conventional Si wafer, it is difficult to produce the apparatus by the above method.
Similarly to the above methods in which the tip of the field emitter is manufactured by using Si or Mo, a study using a method for directly making the tip with the diamond thin film has also been carried out [W. P. Kang, J. L. Davison, Q. Li, J. F. Xu, D. L. Kinser, and D. V. Kerns. 3rd Int. Conf. on Appl. of Diamond Films and Related Materials. NIST. Washington D.C., p37. (1995)]. This is a method in which an Si substrate having a tip-type depressed engraving therein is provided, and after depositing the diamond on the Si substrate, the Si is removed, thereby a diamond tip shaped of an embossed tip can be formed. Although the diamond tip fabricated according to this method is excellent in the field emission characteristic compared with the flat-plate diamond film, there are difficulties in the fabrication process therefor. Specifically, since the diamond tip should have enough thickness to be mechanically support itself in order to prevent the embossed diamond tip from being impaired upon removing Si substrate after the diamond deposition on the Si substrate, thus the thickness of the diamond deposition must be at least hundreds of xcexcm. In this case, it is difficult to uniformly deposit the diamond on the substrate, and when fabricating an field emitter array, the wiring process therefor is almost impossible to achieve.
Additionally, a fundamental problem with the flat-plate diamond film when used as the field emitter is that sparks are generated between the positive and the negative poles when applying a voltage, thus it becomes impossible to use the flat-plate diamond film as a field emitter [O. Groning, O. M. Kuttel, E. Schaller, P. Groning, and L. Schlapbach, Appl. Phys. Lett., 69, 476 (1996), K. R. Lee, K. Y. Eun, S. Lee, and D. R. Jeon, Thin Solid Film. 290/291, 171 (1996)].
In summary, when utilizing a diamond for a field emitter, it is important to economically fabricate a field emission array using a large Si wafer, and to grantee uniform field emission of the fabricated field emission array. However, the above described conventional methods have several problems, that is, sparks are generated between the diamond""s positive and negative poles, and the field emission is not uniformly achieved when employing a diamond field emission array in the form of a flat diode type, and when the tip-type diamond is deposited on the substrate, it is difficult to achieve uniform nucleus formation and uniform deposition, and lastly, it is impossible to economically manufacture the field emission array with a large Si wafer.
Accordingly, it is an object of the present invention to provide an improved diamond field emitter and a fabrication method thereof, which obviates the problems concerning a collection effect of electric field and a sparks generated due to the tip-type diamond according to the related art, while still utilizing the conventional semiconductor manufacturing processes. Therefore, in the present invention, a further advantage is that the wiring and packaging skills according to the prior art can be applied to the present invention without any additional development therefor and any modification thereof.
Additional advantages, objects and features of the invention will become more apparent from the description which follows.